The present invention generally relates to securing a member on a shaft. More particularly, the present invention pertains to an attachment device for arresting a member having a substantially cylindrical bore on a cylindrical shaft.
The mounting of different bore-provided machine members, such as fan wheels, belt pulleys and the like, on a cylindrical shaft so that the machine member will not move circumferentially and/or axially relative to the shaft can be effected in a variety of different ways. It is known, for example, to use a keyway in the shaft and/or in the boss or hub of the machine member, and a key inserted in such keyway for preventing relative circumferential movement between the shaft and the machine member. However, this requires machining the keyway in the shaft. In addition to increasing the manufacturing cost, this process has a tendency to reduces the strength of the shaft. Also, this process is not well suited to being used together with light and inexpensive hollow shafts.
Similar limitations exist with respect to the use of thread joints as this requires thread cutting of the shaft and the inner surface of the bore in the machine member.
The mounting described above can also be achieved using a tapering adapter sleeve. However, this requires that either the shaft or the bore of the machine member have a corresponding taper, thus increasing the manufacturing costs.
Cylindrical shaft and hub joints can also be obtained through the use of a press fit effected with or without the use of a pressure oil arrangement. This alternative is difficult to use with hollow shafts due to large radially inwardly directed forces.
A clamping device addressing at least some of the aforementioned has been employed. This device, named Ringfeder(copyright), manufactured by Ringfeder GmbH, Krefeld, Germany, consists of pairs of ring members having a short axial extension and mating tapering surfaces. A first closed ring member of the pair has a cylindrical bore intended to be arranged in contact with the envelope or outer surface of the shaft and a tapering surface on its opposite side. The second closed ring member of the pair has a cylindrical outer envelope surface intended to contact the cylindrical bore of the member to be attached to the shaft. This second ring member has a bore taper substantially corresponding to that of the outer surface of the first ring member. When the first ring member of the pair has been fitted on the shaft and the second ring member has been loosely fitted thereabout, and also loosely inside the bore of the machine member to be fitted, it is possible to achieve a good grip between the two ring members and, via the intermediary of those ring members, also between the shaft and the machine member. This grip is achieved by pushing the second ring member axially along the external envelope surface of the first ring member, thereby gradually increasing the radial width of the two ring members. For further increasing the retaining force between the shaft and machine member, the pair of Ringfeder(copyright) rings can then be multiplied for achieving the desired grip. The first ring members of the consecutive pairs of ring members are thus positioned with their adjacent gable faces engaging each other and also the second ring member in the adjacent pair. The axial force required for mutually displacing the ring members is obtained by way of a flange ring which is moved axially towards the machine member by being acted upon by screws tightened in threaded bores in the machine member.
Due to the fact that the pairs of ring members are not interconnected, the risk of misalignment exists because the ring members are not centered. This means that the establishment of the grip between the shaft and the machine member might vary from one occasion to another, a result that is undesirable. The plurality of separate elements, i.e. a number of pairs of separate ring members, also makes stocking and handling of these attachment mechanisms extensive and cumbersome.
A need thus exists for an attachment mechanism that is not as susceptible to the same disadvantages and drawbacks as discussed above.
It would be desirable to provide an attachment mechanism that, in a relatively simple and efficient manner permits interconnection of a cylindrical shaft and a machine member having a cylindrical bore, without the need for machining the components to close tolerances and without experiencing drawbacks and disadvantages associated with earlier solutions such as discussed above.
According to one aspect of the invention, a machine member having a substantially cylindrical bore is mounted on a substantially cylindrical shaft, and a stop is provided on the machine member. The bore in the machine member has an inner diameter that is larger than the outer diameter of the shaft so that an annular space exists between the machine member and the shaft. A pair of elements is positioned in the space and have mating, cooperating taper surfaces facing each other. At least one of the elements is movable for displacement relative to the other element to change a radial size of at least one of the elements and thereby increase or reduce a clamping force between the machine member and the shaft. The pair of elements includes a first thin-walled sleeve member enclosing a portion of the shaft and having an outer surface and a smooth inner surface, and a second thin-walled sleeve member engaging the bore of the machine member and having an inner surface and a smooth outer surface. The second sleeve member encloses the first sleeve member. The outer surface of the first sleeve member and the inner surface of the second sleeve member have a plurality of saw-tooth-shaped axially tapering sections. The second sleeve member has one end edge abutting against the stop, and an end edge of the first sleeve member projects outside the opposite end edge of the second sleeve member for receiving an external pushing force causing the at least one element to be displaced relative to the other element to cause the displacement.
According to another aspect of the invention, an arrangement includes a machine member having a substantially cylindrical bore mounted on a substantially cylindrical shaft, and a first sleeve member and a second sleeve member positioned in a space located between an inner surface of the bore in the machine member and an outer surface of the shaft. The first sleeve member has a surface provided with saw-tooth-shaped axially tapering sections and the second sleeve member has a surface provided with saw-tooth-shaped axially tapering sections. The saw-tooth-shaped axially tapering sections of the first sleeve member engage the saw-tooth-shaped axially tapering sections of the second sleeve member. One end edge of the second sleeve member extends axially beyond the one end edge of the first sleeve member and engages a stop. At least the first sleeve member is axially movable relative to the second sleeve member to cause the saw-tooth-shaped axially tapering sections of the first sleeve member to move along the saw-tooth-shaped axially tapering sections of the second sleeve member to increase or decrease a clamping force between the machine member and the shaft. In addition, the second end edge of the first sleeve member extends axially beyond the second end edge of the second sleeve member for receiving an external pushing force causing the first sleeve member to be displaced relative to the second sleeve member.
According to a further embodiment of the invention, an attachment device for arresting a machine member having a substantially cylindrical bore on a cylindrical shaft includes a pair of elements adapted to be positioned in a space between an outer surface of the shaft and an inner surface of the bore in the machine member. The elements have mating cooperating taper surfaces facing each other, with at least one of said elements being movable for displacement relative to the other element to change the radial size of at least one of the elements. The pair of elements includes a first thin-walled sleeve member adapted to encircle a portion of the shaft and having an outer surface and a smooth inner surface. The pair of elements also includes a second thin-walled sleeve member adapted to engage the bore in the machine member and having an inner surface and a smooth outer surface. The second sleeve member encloses the first sleeve member. The outer surface of the first sleeve member and the inner surface of the second sleeve member possess a plurality of saw-tooth-shaped axially tapering sections. An end edge of the first sleeve member projects axially beyond an adjacent end edge of the second sleeve member for receiving an external pushing force causing the first element to be displaced relative to the second element to cause said displacement.